gnu makefile: if condition inside multirow assignment - makefile

Question

Is it possible to have if condition inside multiple-rows assignment of a variable?
The following code triggers an error:
MY_FILES= \
Path/To/IncludeFolder_1 \
ifeq ($(USE_ALTERNATIVE),1) \
Path/To/IncludeFolder_2a \
else \
Path/To/IncludeFolder_2b \
endif \
Path/To/IncludeFolder_3 \
Result:
/bin/sh: -c: line 0: syntax error near unexpected token `('
make: *** [target] Error 2
But the following code also triggers an error:
MY_FILES= \
Path/To/IncludeFolder_1 \
ifeq ($(USE_ALTERNATIVE),1)
Path/To/IncludeFolder_2a \
else
Path/To/IncludeFolder_2b \
endif
Path/To/IncludeFolder_3 \
Result:
Makefile:4: *** missing separator. Stop.
"make" terminated with exit code 2. Build might be incomplete.
If not possible, are there other simple alternatives to achieve this? The use case is a long list of include folders, which can have differences from place to place in function of some defines.

Answer 1

You're making this too complicated.
MY_FILES := Path/To/IncludeFolder_1
ifeq ($(USE_ALTERNATIVE),1)
MY_FILES += Path/To/IncludeFolder_2a
else
MY_FILES += Path/To/IncludeFolder_2b
endif
MY_FILES += Path/To/IncludeFolder_3

Answer 2

You can craft a string-comparison function with relative ease yourself, so that you can facilitate the $(if ) builtin function:
###### $(call str-eq,_string1_,_string2_)
## Compare two strings on equality. Strings are allowed to have blanks.
## Return non-empty if string $1 and $2 are identical, empty string otherwise.
## - `$(call str-eq,yes,no)` --> ` ` (empty string)
## - `$(call str-eq,yes ,yes)` --> ` ` (empty string)
## - `$(call str-eq,yes ,yes )` --> `t`
str-eq = $(if $(subst x$1,,x$2),,t)
MY_FILES= \
Path/To/IncludeFolder_1 \
$(if $(call str-eq,$(USE_ALTERNATIVE),1) \
Path/To/IncludeFolder_2a, \
Path/To/IncludeFolder_2b \
) \
Path/To/IncludeFolder_3
The str-eq and many more utility functions can be found at https://github.com/markpiffer/gmtt.